**6.2 Conditioning: Target L gas**

Two different L gas target properties have been described. Because of their basic constitutions, one bio-methane mixture is conditioned with air and the other is conditioned with a combination of air and LPG.

Table 14 shows a summary of the admixtures with which a target calorific value-oriented mixture for the low calorific base gas property can be achieved.

In the case of simple air addition, particular attention should be paid to compliance with the maximum O2 volume fraction. This should not exceed 3 % vol. in dry networks according to DVGW worksheet G 260. This quantity is reached when adding pure air to the processed biogas, at an admixture of 15 vol -% of air. In the low caloric L gases (e.g. Weser Ems gas), this limit is never reached.

Furthermore, a minimum air addition may also be necessary, in order to achieve the required Wobbe Index according to DVGW worksheet G 260.

Conditioning of Biogas for Injection into the Natural Gas Grid 393

0 2. 4 6 8

94 2 - 4 4 - 7 7 - 10 10 - 14 14 - 16 96 5 - 5 7 - 9 9 - 12 12 - 16 16 - 16

98 - 10 - 11 11 - 15 14 - 16 - 99,5 - 12 - 13 13 - 15 16 - 16 -

**LPG - addition [Vol -%]** 

Table 16. Air addition, depending on the addition of LPG and methane concentration

DIN 51622 "Liquid Gases: Propane, Propene, Butane, Butene and Mixtures Thereof;

DVGW Worksheet G 262 "Use of Gases from Renewable Sources in the Public Gas Supply",

DVGW Worksheet G 486 "Gas Quantity Measurement, Compressibility Factors and Gas

DVGW Worksheet G 685 "Gas Billing incl. First Supplementary Sheet of April 1995 ", April

DVGW Worksheet G 685-2-B "Second Supplementary Sheet to DVGW Worksheet G 685 -

EASEE-gas, Common Business Practice, No. 2005-001/01 "Harmonisation of Natural Gas

Höner zu Siederdissen, Jürgen and Friedrich Wundram "Retrograde Condensation in

Jaeschke, M., P. Schley, "Calculation of the Compressibility Factor of Natural Gases with the

Law on Electricity and Gas Supply (Energy Industry Act - EnWG) EnWG Issue Date: 07.07.

Position Paper of the PTB-AG 1.42 "Gas Measuring Equipment" and AG 3.41 "Caloric Values" on the subject of "Injecting Biogas into Networks", of 6.12.2006

2005 Full quote: "Energy Act of 7 July 2005 (Federal Law Gazette I p. 1970 (3621)), as last amended by Article 2 of the Act of 18 December 2007 (Federal Law Gazette I

Retrograde Condensation Behaviour of some European Natural Gases", Reprint

Natural Gas Transmission Systems", gwf-Gas/Erdgas , 127 (1986)

AGA8-DC92 Equation of State", gwf-Gas/Erdgas 137 (1996) No. 7

p. 2966)" Version: as last amended by Section 2 G v.18.12. 2007 I 2966 Oellrich, Lothar R., Thorsten Engler, Heribert Kaesler and Jens Nixdorf, "Studies of

Quantity Splitting within One Billing Cycle", December 2004, DVGW Worksheet G 685-3-B " third supplementary sheet to DVGW Worksheet G 685 - Substitute Values

DIN 51 624 "Automotive Fuels - Natural Gas Requirements and Test Methods"

DVGW Worksheet G 260 "Gas Properties", January 2000 and May 2008

Law Deviation Factors of Natural Gases" August 1992

of Billing-Related Gas Data ", December 2004

from gwf-Gas/Erdgas 137 (1996) issue 1 page 1-6,

**Methane concentration** 

**in the Vol -%** 

**Holland II HS,n = 9,996 - 10,404 kWh/m³**

**7. References** 

Requirements"

November 2004

1993,

Quality"

GASCALC program, E.ON Ruhrgas

Table 15 shows the minimum air addition for the individual processing grades of methane to achieve an L gas compliant Wobbe Index of under 13.0 kWh/m³ (NTP).


Table 14. Air additions to the H gas properties under investigation


Table 15. Minimum quantity of air to attain L gas specification

For the high-caloric L gas mixtures (target properties according to Holland II L gas) the processed biogas is conditioned with air and LPG. Table 16 shows the correlating LPG-air additions, to reach the calorific value range (+ / -2%).

The gray-shaded areas show where a compliant combination of air and LPG additions is impossible. With increasing LPG additions, the necessary addition of air is limited by the maximum O2 volume fraction of 3 %. If too little LPG is added, only the lower calorific value range can be covered. The broadest coverage of the calorific value range lies in between and is marked by the wider bandwidth of air additions.


Table 16. Air addition, depending on the addition of LPG and methane concentration
